Re: The Paradox of Speciation



Kermit wrote:
On Dec 4, 12:50 pm, treusd...@xxxxxxxxx wrote:
Kermit wrote:
On Dec 3, 7:59 pm, treusd...@xxxxxxxxx wrote:
Kermit wrote:
On Dec 3, 12:35 pm, treusd...@xxxxxxxxx wrote:
Ernest Major wrote:
In message
<9af2e9a4-42e6-441e-81d5-eaf969327...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
treusd...@xxxxxxxxx writes
Ernest Major wrote:

<snip>

Are you conceding the argument? A strong tendency to be selected against
is insufficient to support your contention that speciation is
paradoxical. (And apart from your present use of "strong tendency", I
don't see how your argument differs from my summary thereof. In
particular if you aren't claiming that "Any mutation which causes the
slightest reduction in fertility between members of a population is
selected against." I don't see where you have an argument at all.)

Rephrase for redundant clarity: Discontinuity of reproductive
compatibility over time is paradoxical in the context of natural
selection because such a development works against the fitness of the
individual.

Why? With whom do you think they would be courtin' and sparkin'?

Individuals of their own generation, with whom they loose reproductive
touch by abandoning the commonly inherited basis of reproductive
compatibility.

Why would an organism abandon reproductive compatibility?

It wouldn't, at least as far as natural selection is concerned.

Why would an organism that is better suited to deal with a *completely
*unrelated factor in the environment be less suited to reproduce than
a contemporary which isn't better adapted?

Despite the organism's better overall suitability, its reproductive
biology has decreased compatiblity.

Why? Why would, say, a thicker coat of fur impact its RC any more than
its thinly furred cousin?

In itself it wouldn't.

If the thicker fur is selected because of changes in the climate, why
would this lead to reduced RC than not thicker fur? And if a trait
were selected for that incidentally would be associated with RC (e.g.
size - bigger animals can handle the cold better), then the
inconvenience would be trivial for any one generation, but the
advantages of a healthier mate considerable.

Okay.

*All organisms in each generation would have multiple mutations. Why
do you think that better adaptation would be associated with a lower
RC (repro..etc.)?

It wouldn't, necessarily. A better adapted reproductive biology is
more compatible.

Why do you think that a phenotype which would be selected for would
have a lower RC than a phenotype which would not be selected for?

On that basis alone it wouldn't.

We're not talking about greater differences than average in any one
generation; we're talking about accumulated differences over many
thousands of generations.

Agreed. The dymanics of reproductive adaptiveness are essentially the
same over large and small time intervals.

We humans have about 200 mutations each. Every one of us. If I am
better suited to the environment (say, stronger resistance to a plague
going around), why do you think I would be farther from the average RC
than someone who is not?

You wouldn't necessarily be. Only mutations governing compatibility of
reproductive biology are relevant to reproductive compatibility.

Right. But you said it would be a problem.

I shouldn'ta.

And "fitness" in evolutionary theory is usually defined as an
inheritable characteristic which leads to a reproductive advantage. We
are well aware that there are occasional mutations which do not lead
to reproductive compatibility, but they are uncommon. Individuals
usually have reproductive advantages for reasons which have nothing to
do *directly with the RC. They don't get eaten, for instance.

The exceptions to this observation are negligible in that they do not
suffice to overcome the long term selective disadvantages concomitant
with producing the range of life observed by known mechanisms.

Why is it disadvantageous for me to be unable to reproduce with my
remote ancestors?

Because you simultaneously become unable to reproduce with those of
your own generation who can still reproduce with your remote
ancestors.

No. I have the advantage of all of the genes from all of the mutations
in the last 100,000 or so generations between us and the last
ancestral pool with which we might be incompatible. As are all my
contemporaries. There is no small select group of us evolving while
the rest of the genepool remains stagnant.

Unless we're were isolated - usually geographically. In that case the
species splits. But I still have my peers who are as "evolved" as I.

What if you somehow pass around this backward incompatible trait to
everyone else in your generation?

Pass around? By mating with all the females in my genepool? Guess what
- all of the kids would be compatible with each other. Pardon me, but
you seem really confused about this. As inheritable characteristics
selected by environmental conditions spread thru the genepool, any
incidentally associated changes get passed on also.

That doesn't fix the problem. If you carry mutations to your biology
of reproduction that make you nonviable within the reproductive scheme
inherited by your group, encountering the same defect in a mate
doesn't necessarily fix the problem any more that inflicting the same
damage on two modems restores their ability to communicate.

Nobody has suggested that deviations in sexual apparatus or behavior
necessarily leads to reproductive advantages. But:
1. It might. Not all differences hurt. Some make an organism sexier or
otherwise more successful. A mate that smells better, or sings better,
or a female amphibian that lays eggs a little more resistant to drying
out...

Sexier? That's sexual selection. I'm talking about compatibility of
reproductive biology.

2. Most mutations that would be selected for don't affect RC, or if
they do (like size changes) they don't adversely affect it nearly as
much as the other trait being selected *for.

Absolutely.

Wolves and grizzlies are distant cousins; they cannot mate not for
reason of sexual equipment but because of all the other changes since
their last common ancestor. Unless sexual equipment or behavior is
changed thru adaptive pressures, they are unlikely to change much.

Reproductive incompatibility is not only a matter of "equipment". It
also involves the biology of gestation.

Yes, of course. Once two populations become isolated for whatever
reason, they are free to drift in different directions without having
to worry about being incompatible with their distant cousins across
the river.

But they would still have to worry about being incompatible with each
other, which is a closely related phenomenon.

You may be talking about one of the reasons why geographical isolation
is the most common reason for the divergence of a species into two.

I wonder if you can cite me a specific example of such a divergence
wherein the two were incapable, even if they tried, of producing
offspring.

Then your situation is at least as
bad and probably worse, because why would the simultaneous presence of
your specific incompatibility in a mate necessarily create a new
compatibility scheme to replace the inherited one it has destroyed? It
wouldn't, except by the most improbable chance.

You seem to be picturing dramatic changes, some sort of X-men hopeful
monsters. No - the differences are already there, in every generation
you see of church members, pets, farm animals, and the song birds
outside your window.

What is that supposed to mean?

You keep talking about the lower RC of an individual being selected by
the environment, as though it would be different from the others in
his generation. I can't imagine why you would think that, unless you
are imagining some significantly greater difference from the others.
He wouldn't be - the selected individual is no more different,
ordinarily, than the average difference shown by his contemporaries.

Imagine that X is the mutant superpower, um, characteristic selected
for in any generation (smells slightly better, or slightly thicker
coat).
RP is the cluster of *average reproductive compatiblility
characteristics.

For every generation, there is one or more X being selected. All of
the individuals in that generation show an average deviance from RP.
There is no reason to think that the X individuals show greater
deviance than the average. If the species is well-adapted, there may
be no evolution going on to speak of except some trivial genetic
drift.

But if there is one or more X characteristics, then X rapidly
accumulates in the population, from generation to generation. The
average deviance from RP may change (either from drift or from
incidental small differences associated with X - such as size), but
again, in each generation, the X individuals do not show greater than
average deviation from RP.

To the extent I followed that, you seem to be rapidly changing the
channel between environmental, sexual and (what I have labeled here)
reproductive selection, blurring the three.




3) Therefore once reproductively connected populations cannot diverge in
traits related to reproduction. [Non sequitur: ignores the possibility
of emergent reproductive incompatibilities resulting from the
interaction of neutral changes in each lineage.]

The same "neutral changes" reducing backward compatibility (whenever
and to whatever extent) do likewise to contemporary compatibility.
Since virtually the only source of mutual compatibility within the
current generation is common inheritance, the correlation (not
causation) between the two interfertilities is nearly perfect.

Wrong. The neutral changes do not affect contemporary compatibility -
that's why the word emergent was in the paragraph.

Then they don't effect backward compatibility either.

4) And therefore speciation can't happen. [Non sequitur, based on
repetition of the initial faulty premise: ignores potential selective
pressure for reproductive isolation between ecologically differentiated
populations.]

The "selective pressure for reproductive isolation" acts on the entire
phenotype. That doesn't make reproductive disjunction within a
population advantageous.

But reproductive disjunction within populations has been observed to be
advantageous. See Galapagos ground finches again.

To guess at your meaning, that's geographic isolation. No the same
thing as incompatibility.

But no organism in any generation shows accumulated reproductive
incompatibility. If, for instance, the climate turns colder, then the
sexually mature individuals who are thriving because they are furrier
or bigger of shorter-limbed or better hunters will be desirable mates.
There is no reason to assume that they would be less reproductively
successful because they are better adapted to the cold than their
peers. If anything they would be sexier and better able to reproduce
than those shivering losers in the back row. Backward compatibility is
not an issue - most organisms do not attempt reproduction with their
great-great-great-grandparents.

Backward and contemporary compatibility go together, because the
former is the source of the latter. The former confers no advantage in
itself.

Stuff and nonsense. the ancestor may explain the descendants to a
large degree, but the descendants do not care one whit about their
ancestors; only their immediate environment.

Naturally.

Hmm. Maybe I misread what you were getting at here.


Why is backward compatibility necessary?

It's not, but it follows from contemporary compatibility.

Yeah... but drift or association with the selected traits may lead to
great differences. There are some here who will not call a genepool
which differs significantly from their predecessors a different
species, for this reason. If you had a time machine, they might be RC.


And why do you think that RC changes are associated with unrelated
characteristics?

I don't.

Then why would it be a problem?

The group gets its collective scheme of compatible reproductive
interaction from its predecessors. Once this commonly inherited RC
goes (for whatever reason), there's nothing to replace it with.

Of *course if any organism shows reproductive incompatibility to any
noticeable degree it will not likely pass his genes on - it's all
about reproductive success.

I suspect that any potential rival that actually *dies is probably not
very reproductively compatible with potential mates.

Apparently I didn't emphasize this enough in my first post. The real
gist of my claim concerns the reproductive advantage of compatible
reproductive morphology. When you bring up how natural selection acts
on the unified phenotype, that's really not addressing my point.

You seem to think that your confusion of ideas is a problem for
evolutionary theory. I can hardly ignore the central concept of the
theory in this context.

You're so witty.

Just the opposite. I can't understand you, but you're not an idiot. So
are you confused, or can I not read for comprehension?

Most of the fault lies with my choice of terminology.

In your OP you said "Insofar as a mutation contributes to speciation,
it also, by definition, reduces reproductive compatibility with
available mates and is thus detrimental to fitness."

Do you still stand by that?

Oh yeah. I would phrase it somewhat differently now, but you seem to
get it.

Let's try this: we both think that speciation means a species changes
over time, or more often splits, so that the two genepools will not
ordinarily reproduce successfully, yes?

That's right. Except, for the sake of total clarity, say "cannot
reproduce successfully".

I think that actual selection for traits which do not improve RC does
not normally happen. They may be incidentally associated with traits
which improve reproductive fitness for other reasons, and are then
indirectly selected for. But more often a population is split by
geography or sometimes two different strategies for coping with the
environment. Once that happens, they are free to drift in different
directions, or select traits which may affect RC (like size), and in
time become incompatible.

The last sentence is where we disagree. The scheme of compatible
reproductive interaction the founder group brings with them to
Gilligan's Island is, like the Professor's transistor radio, the only
one they'll ever have unless the selection pressure acting to
collectivize their biology of reproduction is not the only
evolutionary influence.

Normally they are not selected *because they are incompatible; they
are instead *able to become incompatible because they are no longer
interbreeding for other reasons.

Kermit

How could the reproductive system contribute more significantly to the
fitness of the individual than by being as reproductively compatible
as possible with prospective mates?

.

Relevant Pages

  • Re: Reproductive Selection
    ... there is no need to "generate compatibility". ... alive today that require RC in order to reproduce can be traced as far ... You'd probably call that reproductive selection. ... had NO other effect other than to lower fertility. ...
    (talk.origins)
  • Re: The Paradox of Speciation
    ... compatibility over time is paradoxical in the context of natural ... at least as far as natural selection is concerned. ... *unrelated factor in the environment be less suited to reproduce than ... Reproductive incompatibility is not only a matter of "equipment". ...
    (talk.origins)
  • Re: Reproductive Selection
    ... there is no need to "generate compatibility". ... alive today that require RC in order to reproduce can be traced as far ... You'd probably call that reproductive selection. ... Changes that slightly reduce fertility ...
    (talk.origins)
  • Re: The Paradox of Speciation
    ... Why would "backward compatibility" be valuable? ... distant ancestors implies incompatibility with your contemporaries. ... statistical likelihood that your "young'uns" will survive to reproduce ... more than young without the variation, natural selection will favor ...
    (talk.origins)
  • Re: The Paradox of Speciation
    ... compatibility over time is paradoxical in the context of natural ... *unrelated factor in the environment be less suited to reproduce than ... remote ancestors? ... your specific incompatibility in a mate necessarily create a new ...
    (talk.origins)